CN101931107B - Electrolyte solution for electrochemical device and electrochemical device thereof - Google Patents

Abstract

The present invention provides an electrolyte for an electrochemical device containing a novel additive and an electrochemical device thereof. The additive is a compound shown in a chemical formula :

wherein R is as defined herein and n is an integer of 2, 3 or 4. The additive can protect the surface of an anode carbon material in a battery, inhibit the occurrence of a disintegration phenomenon and prolong the service life of the battery.

Description

Electrolyte solution for electrochemical device and electrochemical device thereof

technical field

The present invention relates to an electrolytic solution for an electrochemical device, in particular to an electrolytic solution that helps to suppress the disintegration of battery materials and an electrochemical device with the electrolytic solution.

Background technique

In recent years, research on energy storage technologies has increased. Batteries have been widely used in mobile phones, camcorders, notebook computers, etc., and Chinese people have invested a lot of research on this. Among them, the secondary battery (secondary battery) has aroused great interest. The main research direction for secondary batteries is to improve their energy density and cycle life.

Among the currently used secondary batteries, lithium ion secondary batteries were developed in the 1990s. Compared with traditional batteries using aqueous electrolytes (such as nickel-hydrogen batteries, nickel-cadmium batteries, and lead-acid batteries), lithium-ion secondary batteries have higher working voltage and energy density, so in secondary batteries lead to more research. However, a lithium-ion secondary battery has a disadvantage in that its quality deteriorates during repeated charging and discharging. This problem will become more serious as the capacity of the lithium ion secondary battery increases. Therefore, the service life of lithium-ion secondary batteries needs to be further improved, and generally the main direction is to improve the electrolyte.

Most of the electrolytes of lithium-ion secondary batteries use organic carbonates as solvents. According to their structures and characteristics, they can be divided into two categories: (1) cyclic carbonates, such as ethylene carbonate (EC) and Propylene carbonate (PC), etc., which have high dielectric constant and viscosity characteristics; (2) chain carbonates, such as dimethyl carbonate (dimethyl carbonate, DMC), diethyl carbonate (diethyl Carbonate, DEC) and methyl ethyl carbonate (ethyl methylcarbonate, EMC), etc., these components have the characteristics of lower dielectric constant and viscosity. An ideal electrolyte must have both a high dielectric constant and a low viscosity, so common electrolytes contain both high dielectric constant cyclic carbonates and low viscosity chain carbonates.

However, EC and PC have the following characteristics: (1) EC will form a good passive film on the anode surface of the battery during the first charging process, while PC, DEC, DMC and EMC cannot form a good passive film. However, the melting point of EC is as high as 37 degrees Celsius, which will cause poor charge and discharge performance of the battery at low temperature. (2) The melting point of PC is -49 degrees Celsius, and it still has good fluidity at low temperatures, but PC is easy to "co-intercalate" with lithium ions and enter the carbon layered structure. When the potential reaches When the reduction potential of PC is lowered, PC will undergo reductive cracking, and at the same time, gas will be generated to cause structural damage to the anode, so too high a PC content will often result in a reduction in battery life.

In order to solve the above problems, most of the general commercial electrolytes use a mixed solvent of EC and PC to avoid the above disadvantages and improve the performance of the battery; in addition to adjusting the ratio of solvent components, the use of additives is used to improve battery life, capacity and The most effective method for low-temperature performance; however, common additives such as vinylene carbonate, sulfites, sulfates, phosphate esters or their derivatives are not only expensive , the effect is not satisfactory.

In this regard, Japanese Patent Publication No. 2002-158034 discloses an acrylic acid compound as an additive to the electrolyte solution of a lithium-ion secondary battery. The acrylic acid additive can suppress gas generation and anode degradation in lithium-ion secondary batteries. In addition, Japanese Patent Publication 2003-168479 discloses an acrylic compound having at least three acrolein groups as an additive to the electrolyte of a lithium-ion secondary battery, which can produce a solid electrolyte interface film via a reduction reaction on the anode (SEI film, solid electrolyte interface layer). The SEI film can inhibit the decomposition reaction of the electrolyte on the anode, thus increasing the lifespan of the battery. In addition, WO 2008/050971 discloses an acrylic compound having a polymerizable double bond as an electrolyte additive for lithium-ion secondary batteries, which also has the effect of forming an SEI film.

People look forward to developing novel lithium-ion secondary battery electrolyte additives on the basis of existing technologies, which help to form a structurally stable SEI film on the surface of carbon materials, inhibit the disintegration of carbon materials, and further improve lithium-ion secondary battery electrolyte additives. battery life.

Contents of the invention

In view of the lack of prior art, the object of the present invention is to provide an electrolyte for electrochemical devices (such as lithium-ion secondary batteries), through the new additive components in the electrolyte to make the surface of the anode carbon material form a stable structure The SEI film can inhibit the occurrence of disintegration and improve the life of the battery. Moreover, the electrolyte helps to slow down the capacitance decay of the cathode sheet during charging and discharging, and maintain better performance for a long time.

Another object of the present invention is to provide an electrochemical device using the electrolytic solution. The electrolyte contains novel additives, which can form a structurally stable SEI film on the surface of the anode carbon material to inhibit the occurrence of disintegration and improve the life of the battery. Moreover, the electrolyte helps to slow down the capacitance decay of the cathode sheet during charging and discharging, and maintain better performance for a long time.

In order to achieve the above object, the present invention provides a kind of electrolytic solution for electrochemical devices, which comprises: 1.18-35.4% by weight of electrolyte; 0.1-9.0% by weight of the compound shown in chemical formula (I); organic solvent, which is Used to make up the aforementioned electrolyte to 100% by weight,

Wherein, R is an aliphatic or aromatic group that is unsubstituted or substituted by one or more substituents, n is an integer of 2, 3 or 4, wherein the above-mentioned substituents are selected from one or more halogens, C ₁ -C ₈ alkyl, C ₁ -C ₈ alkoxy, C ₆ -C ₁₀ aryl, C ₆ -C ₁₀ aryloxy, C ₃ -C ₆ cycloalkyl, C ₃ -C ₆ cycloalkoxy, C A group consisting of ₁ -C ₃ carboxyl and thio groups, wherein one or more methylene groups (-CH ₂ -) in the above-mentioned aliphatic or aromatic groups can be independently replaced by an oxygen atom (-O-) , C ₆ -C ₁₀ aryl, C ₆ -C ₁₀ cycloalkyl, replacement.

When the compound represented by the chemical formula (I) is used as an electrolyte additive, a special SEI film can be formed on the surface of an anode carbon material of an electrochemical device (such as a lithium ion secondary battery). This special SEI film can not only protect the carbon material structure, but also inhibit the disintegration phenomenon caused by repeated charging and discharging, and improve the battery life. Moreover, compared with the commonly used additives PS (propane sultone) and VC (vinylenecarbonate), this new additive can not only improve the tolerance of carbon materials in PC electrolyte, but also achieve the protection effect of carbon materials with less addition. In addition, the additive helps to slow down the capacitance decay of the cathode sheet during charge and discharge, and maintain better performance for a long time.

Preferably, the electrolytic solution of the present invention comprises a compound represented by the following chemical formula:

Some of the compounds shown in the chemical formula (1) of the present invention are commercially available, and the other part can be synthesized by existing organic synthesis methods, such as BUNGOOCHIAI, SHOKO INOUE, TAKESHI ENDO, etc. in "One-Pot Non-Isocyanate Synthesis of Polyurethanes from Bisepoxide, Carbon Dioxide, and Diamine" (Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 43, 6613-6618 (2005)) and the synthetic method disclosed in Nobuhiro Kihara, Yuichi Nakawaki and The synthetic method disclosed in "Preparation of 1,3-Oxathiolane-2-thiones by the Reaction of Oxirane and Carbon Disulfide" (J.Org.Chem.1996, 60, 473-475) by Takeshi Endo et al.

In the electrolyte solution provided by the present invention, preferably, the content of the compound represented by the aforementioned chemical formula (I) is 0.5 to 5.0% by weight.

In the electrolyte solution provided by the present invention, preferably, the content of the aforementioned electrolyte is 5.9-23.6% by weight.

In the electrolyte solution provided by the present invention, preferably, the aforementioned organic solvent is selected from the group consisting of cyclic carbonates, linear carbonates, lactones, ethers, esters A group consisting of esters, acetonitrile, lactams, ketones and their halogen derivatives, that is, one or more of the above-mentioned solvents. More preferably, the organic solvent is a mixture of cyclic carbonates and linear carbonates.

In the electrolyte solution provided by the present invention, preferably, the cation of the aforementioned electrolyte is selected from the group consisting of Li ⁺ , Na ⁺ and K ⁺ , that is, one or more of the aforementioned cations; the anion of the aforementioned electrolyte selected from PF ₆ ^- , BF ₄ ^- , Cl ^- , Br ^- , I ^- , ClO ₄ ^- , AsF ₆ ^- , CH ₃ CO ₂ ^- , CF ₃ SO ₃ ^- , N(CF ₃ SO ₂ ) ₂ ^- and C(CF ₂ SO ₂ ) ₃ ^- , that is, one or more of the above-mentioned anions.

The present invention also provides an electrochemical device, which comprises: a cathode; an anode; and the electrolyte of the present invention.

According to the specific technical solution of the present invention, preferably, the above electrochemical device is a lithium ion secondary battery.

The present invention also includes a use of the compound represented by the chemical formula (I) as an additive in the electrolyte, that is, the use of the compound represented by the chemical formula (I) as an additive for the electrolyte.

As described above, the electrolytic solution for electrochemical devices of the present invention uses novel additive components. The additive can form a special SEI film on the surface of the anode carbon material to inhibit the occurrence of disintegration, improve the life of the battery, and has the effect of slowing down the capacity fading on the cathode; compared with traditional electrolyte additives (such as PS (propane sultone) or VC (vinylene carbonate)) has a better effect of inhibiting disintegration.

Description of drawings

Fig. 1A is the battery charging and discharging test result of embodiment 1 of the present invention;

Fig. 1B is the battery charge and discharge test result of Comparative Example 2 of the present invention;

Fig. 1C is the battery charge and discharge test result of Comparative Example 3 of the present invention;

Fig. 1D is the battery charge and discharge test result of Comparative Example 4 of the present invention;

Figure 1E is the battery charge and discharge test results of Comparative Example 5 of the present invention;

Fig. 2A is the battery charge and discharge test result of Example 2-1 of the present invention;

Fig. 2B is the battery charge and discharge test result of Example 2-2 of the present invention;

Fig. 2C is the battery charge and discharge test result of Example 2-3 of the present invention;

Fig. 2D is the battery charging and discharging test results of Example 2-4 of the present invention;

Figure 2E is the battery charge and discharge test results of Example 2-5 of the present invention;

Fig. 2F is the battery charging and discharging test results of Example 2-6 of the present invention;

Fig. 2G is the battery charge and discharge test result of Comparative Example 6 of the present invention;

Fig. 3 is the cycle life test result of embodiment 3 of the present invention and comparative example 7;

Fig. 4 is the first lap charge and discharge curves of Comparative Example 8, Embodiment 4-1, 4-2 and 4-3 of the present invention;

Fig. 5 is the first lap charge and discharge curves of Comparative Example 9, Examples 5-1, 5-2 and 5-3 of the present invention;

FIG. 6 is the cycle life test results of Comparative Example 10 and Example 6 of the present invention.

Detailed ways

As described above, the electrolyte solution for electrochemical devices of the present invention uses novel additives. The additive can form a special SEI film on the surface of the anode carbon material. This special SEI film can not only protect the carbon material structure, but also inhibit the disintegration phenomenon caused by repeated charging and discharging, and improve the battery life. Moreover, compared with the existing additives PS and VC, this new additive can not only improve the tolerance of carbon materials in PC electrolyte, but also achieve the protection effect of carbon materials with less addition. In addition, the electrolytic solution of the present invention also has the effect of slowing down the capacitance decay in the process of charging and discharging the cathode sheet, and can maintain better performance for a long time.

The organic solvent used in the electrolytic solution of the present invention is mainly used to supplement the electrolytic solution to 100% by weight. In a preferred embodiment, the content of the organic solvent is 64.5-98.81% by weight, more preferably 76.4-94.1% by weight. Of course, those skilled in the art can change the content according to actual needs. The organic solvent used in the present invention can adopt organic solvents known in the art, such as but not limited to: cyclic carbonates (cyclic carbonates), linear carbonates (linear carbonates), lactones (lactones), ethers (ethers) ), esters (esters), acetonitrile (acetonitrile), lactams (lactams), ketones (ketones) or halogen derivatives of the above compounds. Preferably, a mixture of at least one cyclic carbonate-based organic solvent and at least one linear carbonate-based organic solvent can be used. The mixing ratio of individual organic solvents is not particularly limited as long as it does not interfere with the purpose of the present invention and follows the mixing ratio used to manufacture non-aqueous electrolytes conventionally used for lithium batteries.

The electrolyte used in the electrolyte solution of the present invention is also a well-known electrolyte in the art, and its cations are such as but not limited to: Li ⁺ , Na ⁺ or K ⁺ ; its anions are such as but not limited to: PF ₆ ⁻ , BF ₄ ^- , Cl ^- , Br ^- , I ^- , ClO ₄ ^- , AsF ₆ ^- , CH ₃ CO ₂ ^- , CF ₃ SO ₃ ^- , N(CF ₃ SO ₂ ) ₂ ^- or C(CF ₂ SO ₂ ) ₃ ^- .

The electrolytic solution of the invention is suitable for general electrochemical devices, especially lithium ion secondary batteries.

The following provides the embodiments of the present invention to illustrate the advantages and technical characteristics of the present invention. However, the embodiments are not intended to limit the present invention. Various changes and modifications, therefore, the protection scope of the present invention should be defined by the claims.

Example:

Table 1 shows the additives used in the examples of the present invention, which are only used for illustration, and are not intended to limit the scope of rights of the present invention.

Table 1 The used additive of the embodiment of the present invention

Embodiment 1: use the charging and discharging test of the lithium ion secondary battery of electrolytic solution of the present invention

Example 1 of the present invention was tested using a lithium ion secondary battery system. Table 2 lists the materials and components used in the lithium-ion secondary battery system of Example 1. In addition, the material used in Comparative Example 2 is the same as that of Example 1, except that it does not contain additives; Comparative Example 3 uses 1.0% by weight of PS as an additive; Comparative Example 4 uses 1.0% by weight of VC as an additive. The electrode material used in the present invention and its preparation process belong to the known art. Those skilled in the art can easily understand the technical features of the present invention and implement them according to the foregoing description of the invention, so the detailed preparation process is not specifically described here.

Table 2 Battery structure and materials of Example 1

Note:

NG: natural crystalline flake graphite

PVdF: polyvinylidene difluoride

DEC: diethyl carbonate

EC: ethylene carbonate

PS: 1,3-propane sultone (1,3-propane sultone)

VC: vinylene carbonate

Charge and discharge test

In order to test the charging and discharging performance of the battery system, the battery systems of Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5 were assembled into coin-type batteries (button-type batteries), and connected to an 8-channel charging and discharging instrument . The charge and discharge current is set according to 0.1 C-rate, the charge cut-off voltage is 3mV, and the discharge cut-off voltage is 1800mV. The continuous charge and discharge program experiment is carried out, and 5 charge and discharge cycles are tested, and the voltage change is recorded by computer, and converted by calculation. Get the size of the electric capacity.

FIG. 1A to FIG. 1E show the charging and discharging test results of the batteries of Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 and Comparative Example 5. Among them, Figure 1A shows that Example 1 of the present invention (containing 1% by weight of Compound 1) still maintains good reversible charge-discharge properties after five consecutive charge-discharge tests, and the discharge capacity is higher than 300mAh·g ^-1 ; Figure 1B It shows that comparative example 2 (without additive) disintegrates in the first cycle of charge and discharge test, and the battery cannot be discharged normally in the first discharge cycle; Fig. 1C shows comparative example 3 (containing 1% by weight of PS ) can be charged and discharged normally in the first round of charge and discharge test, but after the second round of charge and discharge test, the charge and discharge capacity decays rapidly, showing that the carbon material disintegrates after the second round of charge and discharge test, and the fifth time The reversible capacity of discharge is only 21mAh·g ^-1 , accounting for less than 7% of the first discharge capacity; Figure 1D shows that Comparative Example 4 (containing 1 wt% VC) collapsed in the first cycle of charge and discharge test Solution, the reversible capacitance of the first discharge is lower than 20mAh·g ^-1 ; Figure 1E shows that Comparative Example 5 (containing 1% by weight of compound 8) can be charged and discharged normally in the first round of charge and discharge test, but the second round of charge After the discharge test, the charge and discharge capacity decayed ^rapidly , indicating that the carbon material disintegrated after the second cycle of charge and discharge test. The ratio is lower than 3%, showing that the structure of compound 8 has no protective effect on carbon materials in high-concentration PC electrolyte. From the above results, it can be seen that the electrolyte solution of the present invention helps to inhibit the disintegration of materials in the battery, thereby improving the service life of the battery.

Embodiment 2: use the charging and discharging test of the lithium ion secondary battery of electrolytic solution of the present invention

Example 2 of the present invention was tested using a lithium-ion secondary battery system. Table 3 lists the materials and components used in the lithium-ion secondary battery system of Example 2. In addition, Comparative Example 6 used 1.5% by weight of VC as an additive.

The battery structure and materials of Table 3 Example 2

Fig. 2A to Fig. 2G show the battery charge and discharge test of embodiment 2-1, embodiment 2-2, embodiment 2-3, embodiment 2-4, embodiment 2-5, embodiment 2-6 and comparative example 6 result. Among them, Fig. 2A shows that Example 2-1 of the present invention (containing 1.5% by weight of compound 2) still maintains good reversible charge and discharge properties after five consecutive charge and discharge tests, and the discharge capacity is higher than 250mAh·g ^-1 . Figure 2G shows that comparative example 6 (containing 1.5% by weight of VC) disintegrated in the first charge-discharge test, and the reversible discharge capacity of the battery was lower than 2mAh·g ^-1 in the first discharge cycle; the second The reversible discharge capacity of the charge-discharge cycle of the first cycle and the fifth cycle is still less than 30mAh·g ^-1 , which is far lower than the actual capacitance of natural graphite materials, showing that the addition of 1.5 wt% VC is still unable to effectively inhibit the natural graphite carbon material at high Concentration PC electrolyte disintegration reaction. It can be seen that the electrolyte additive compound 2 of the present invention helps to inhibit the disintegration of materials in the battery, thereby improving the service life of the battery.

Figure 2B shows that Example 2-2 of the present invention (containing 1.5% by weight of compound 3) has an initial discharge capacity of 306mAh·g ^-1 , and after five consecutive charge and discharge tests, it still maintains good reversible charge and discharge properties, and the discharge capacity reaches 283mAh·g ^-1 . It can be seen that the electrolyte additive compound 3 of the present invention helps to inhibit the disintegration of materials in the battery, thereby improving the service life of the battery.

Figure 2C shows that Example 2-3 of the present invention (containing 1.5% by weight of compound 4) still maintains good reversible charge-discharge properties after five consecutive charge-discharge tests, with a discharge capacity of 286mAh·g ^-1 . It can be seen that the electrolyte additive compound 4 of the present invention helps to inhibit the disintegration of materials in the battery, thereby improving the service life of the battery.

Figure 2D shows that Example 2-4 of the present invention (containing 1.5% by weight of compound 5) still maintains good reversible charge-discharge properties after five consecutive charge-discharge tests, with a discharge capacity of more than 300mAh·g ^-1 . It can be seen that the electrolyte additive compound 5 of the present invention helps to inhibit the disintegration of materials in the battery, thereby improving the service life of the battery.

Figure 2E shows that the first discharge capacity of Example 2-5 of the present invention (containing 1.5% by weight of compound 6) is 160mAh·g ^-1 , and the third discharge capacity can reach 283mAh·g ^-1 . It can be seen that the electrolyte additive compound 6 of the present invention helps to inhibit the disintegration of materials in the battery, thereby improving the service life of the battery.

Figure 2F shows that the first discharge capacity of Example 2-6 of the present invention (containing 1.5% by weight of compound 7) is 260mAh·g ^-1 , and the fifth discharge capacity can reach 278mAh·g ^-1 . It can be seen that the electrolyte additive compound 7 of the present invention helps to inhibit the disintegration of materials in the battery, thereby improving the service life of the battery.

Embodiment 3: use the cycle life test of the lithium ion secondary battery of electrolytic solution of the present invention

Example 3 of the present invention was tested using a lithium ion secondary battery system. Table 4 lists the materials and components used in the lithium ion secondary battery system of Example 3. In addition, the materials used in Comparative Example 7 are the same as those in Example 3, except that no additives are included.

The battery structure and materials of Table 4 Example 3

Note: NG-Sn: natural graphite carbon material modified by electroless tin plating

Cycle life test

In order to test the cycle life performance of the battery system, the battery systems of Example 3 and Comparative Example 7 were assembled into coin-shaped batteries and connected to an 8-channel charging and discharging instrument. Set the charging current according to 0.1 C-rate, the cut-off voltage is 3mV; set the discharge current according to 0.5C-rate, the cut-off voltage is 1800mV, conduct continuous charge and discharge program experiments, test 30 charge and discharge cycles, and use the computer to record the voltage Change, and the size of the capacitance is obtained by calculating the conversion.

FIG. 3 shows the battery cycle life test results of Example 3 and Comparative Example 7. The test results of the cycle life of Example 3 show that the battery capacity is higher than that of Comparative Example 7 (without additives); and after 30 cycle life tests, the capacity of Example 3 is still higher than 300mAh g ^-1 The capacitance of 7 decays to below 50mAh·g ^-1 . This result shows that the additive of the present invention can increase the capacity of the battery, and can effectively improve the cycle life characteristics of the battery.

Embodiment 4: use the charge and discharge test of the lithium ion secondary battery of electrolytic solution of the present invention

Example 4 of the present invention was tested using a lithium ion secondary battery system. Table 5 lists the materials and components used in the lithium-ion secondary battery system of Example 4. In addition, the materials used in Comparative Example 8 are the same as those in Example 4, except that no additives are included.

Battery structure and materials of Table 5 Example 4

Note: MCMB25-28 is a product of Osaka Gas Chemicals (OGC).

FIG. 4 shows the first cycle charge and discharge curves of Comparative Example 8, Examples 4-1, 4-2 and 4-3. Among them, curves 1 and 1' show that comparative example 8 (without additives) disintegrates at the first charge, and the reversible discharge capacity of the battery in the first charge and discharge cycle is only 0.5mAh·g ^-1 , which cannot be charged normally. discharge. Figure 4 curves 2 and 2', 3 and 3' and 4 and 4' respectively show embodiment 4-1 (compound 3 containing 1.5% by weight), embodiment 4-2 (compound 5 containing 1.5% by weight) and implementation In the first cycle of charge and discharge curves of Example 4-3 (containing 1.0% by weight of compound 1), the three sets of curves all show good charge and discharge efficiencies. It can be seen that the electrolyte additive compound 3, compound 5 and compound 1 of the present invention are all helpful to inhibit the material disintegration of MCMB25-28 in the high PC content electrolyte, and improve the charge and discharge performance of the battery anode material.

Embodiment 5: use the charge and discharge test of the lithium ion secondary battery of electrolytic solution of the present invention

Example 5 of the present invention was tested using a lithium ion secondary battery system. Table 6 lists the materials and components used in the lithium-ion secondary battery system of Example 5. In addition, the materials used in Comparative Example 9 are the same as those in Example 5, except that no additives are included.

Battery structure and materials of Table 6 Example 5

Note: MGP is a carbon anode material product of Sinosteel.

Fig. 5 shows the first cycle charge and discharge curves of Comparative Example 9, Examples 5-1, 5-2 and 5-3. Among them, curves 1 and 1' show that comparative example 9 (without additives) disintegrates at the first charge, and the reversible discharge capacity of the battery is lower than 3mAh·g ^-1 in the first charge and discharge cycle, and cannot be charged normally. discharge. Figure 5 curves 2 and 2', 3 and 3' and 4 and 4' respectively show embodiment 5-1 (compound 3 containing 1.5% by weight), embodiment 5-2 (compound 5 containing 1.5% by weight) and implementation In the first cycle of charge and discharge curves of Example 5-3 (containing 1.0% by weight of compound 1), the three sets of curves all show good charge and discharge efficiencies. It can be seen that the electrolyte additive compound 3, compound 5 and compound 1 of the present invention all help to inhibit the material disintegration of MGP in the high PC content electrolyte and improve the charge and discharge performance of the battery anode material.

Embodiment 6: the effect of electrolytic solution of the present invention on cathode sheet

The above Examples 1-5 are for testing the effect of the electrolyte solution of the present invention on the anode sheet. In order to test the effect of the electrolyte solution of the present invention on the cathode sheet, LiFePO ₄ /conductive carbon black/PVdF was used as the cathode; lithium metal was used as the anode for testing, and the detailed materials and their compositions are shown in Table 7. Similarly, the materials and preparation process used for the cathode sheet belong to the prior art, and will not be repeated here.

The battery structure and materials of Table 7 Example 6

The battery system of Example 6 was subjected to charge and discharge cycles at room temperature to test the change of its capacity. The charging conditions are: 1C constant current charging, 4000mV cut-off charging. The discharge conditions are: 1C constant current discharge, 2500mV cut-off discharge. The results of the capacitance change with the number of charge and discharge cycles are shown in Figure 6. Wherein, the material used in Comparative Example 10 is the same as that of Example 6, except that it does not contain additives. It can be seen from FIG. 6 that the electrode system using the electrolyte solution of the present invention can maintain a high capacitance after cyclic charging and discharging.

In summary, the electrolytic solution of the present invention can form a structurally stable SEI film on the surface of the anode carbon material through the use of new additives to protect the surface of the carbon material from the occurrence of disintegration, increase the service life of the battery, and On the cathode sheet, it helps to slow down the reduction of capacitance and maintain better performance for a long time.

other implementations

All the features disclosed in this specification can be combined in any way. Features disclosed in this specification may be replaced by features of the same, equivalent or similar purpose. Therefore, unless the emphasis is specifically stated, the features disclosed in this specification are one embodiment of a series of equivalent or similar features.

In addition, based on the content disclosed in this specification, those skilled in the art can easily make appropriate changes and modifications for different usage methods and situations according to the basic features of the present invention without departing from the spirit and scope of the present invention. Therefore, other implementations The method is also included in the scope of protection of the claims.

Claims (11)

1. An electrolyte solution for an electrochemical device, comprising: 1.18-35.4% by weight electrolyte; 0.1-9.0% by weight of the compound shown in chemical formula (I)

and an organic solvent, which is used to make up the electrolyte to 100% by weight, Wherein, R is an aliphatic or aromatic group that is unsubstituted or substituted by one or more substituents, n is 2, 3 or 4, wherein the substituents are selected from one or more halogens, C ₁ -C ₈ Alkyl, C ₁ -C ₈ alkoxy, C ₆ -C ₁₀ aryl, C ₆ -C ₁₀ aryloxy, C ₃ -C ₆ cycloalkyl, C ₃ -C ₆ cycloalkoxy, C ₁ -A group consisting of C ₃ carboxyl and thio groups, wherein one or more methylene groups in the aliphatic or aromatic group can be independently replaced by an oxygen atom, a C ₆ -C ₁₀ arylene group, C ₆ -C ₁₀ cycloalkylene,

replacement; The electrochemical device is a lithium ion secondary battery. 2. electrolyte solution as claimed in claim 1, wherein, the compound shown in described chemical formula (I) is:

3. The electrolytic solution according to claim 1, wherein the content of the compound represented by the chemical formula (I) is 0.5-5.0% by weight. 4. The electrolytic solution according to claim 1, wherein the content of the electrolyte is 5.9-23.6% by weight. 5. The electrolytic solution according to claim 1, wherein the organic solvent is selected from one or more of ethers, esters, acetonitrile, lactams, ketones and their halogen derivatives. 6. The electrolyte solution according to claim 5, wherein the esters include one or more of cyclic carbonates, linear carbonates and lactones. 7. The electrolytic solution according to claim 5, wherein the organic solvent is a mixture of cyclic carbonates and linear carbonates. 8 . The electrolyte solution according to claim 1 , wherein the cations of the electrolyte are selected from one or more of Li ⁺ , Na ⁺ and K ⁺ . 9. The electrolyte solution according to claim 8, wherein the anion of the electrolyte is selected from PF ₆ ⁻ , BF ₄ ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , ClO ₄ ⁻ , AsF ₆ ⁻ , CH ₃ CO ₂ One or more of ^- , CF ₃ SO ₃ ^- , N(CF ₃ SO ₂ ) ₂ ^- and C(CF ₂ SO ₂ ) ₃ ^- . 10. An electrochemical device comprising an anode, a negative electrode and the electrolyte according to claim 1, the electrochemical device being a lithium ion secondary battery. 11. A use of a compound shown in chemical formula (I) as an additive in the electrolyte; The compound shown in the chemical formula (I) is the compound shown in the chemical formula (I) in claim 1; The electrolyte is the electrolyte of lithium ion secondary battery.

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